Data commit

Task/Straddling-checkerboard/PicoLisp/straddling-checkerboard.l

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+(de *Straddling
+   (NIL  "H"  "O"  "L"  NIL  "M"  "E"  "S"  NIL  "R"  "T")
+   ("3"  "A"  "B"  "C"  "D"  "F"  "G"  "I"  "J"  "K"  "N")
+   ("7"  "P"  "Q"  "U"  "V"  "W"  "X"  "Y"  "Z"  "."  "/")
+   ("79" "0"  "1"  "2"  "3"  "4"  "5"  "6"  "7"  "8"  "9") )
+
+(de straddle (Str)
+   (pack
+      (mapcar
+         '((C)
+            (pick
+               '((L)
+                  (and
+                     (index C (cdr L))
+                     (cons (car L) (dec @)) ) )
+               *Straddling ) )
+         (chop (uppc Str)) ) ) )
+
+(de unStraddle (Str)
+   (pack
+      (make
+         (for (L (chop Str)  L)
+            (let C (pop 'L)
+               (setq C
+                  (if (assoc C *Straddling)
+                     (get (cdr @) (inc (format (pop 'L))))
+                     (get (cdar *Straddling) (inc (format C))) ) )
+               (link (if (= "/" C) (pop 'L) C)) ) ) ) ) )